1. Field of the Invention
The invention relates generally to the field of manufacturing and processing of product in particle form, such as pellets. More specifically, the invention relates to apparatus for cooling, removal of fines and dust, and classification of pelletized product after forming the product.
2. Background Art
Products in the form of particles or pellets may be made, for example, by extrusion of material heated near above its fusion temperature among other processes. Examples of such materials include thermoplastic. After extrusion and cutting to selected lengths, the product pellets may be subjected to processes such as removal of small size material particles, referred to as “streamers”, “ribbons” and “angel hairs.” The product pellets may also be cooled, have dust removed from the exterior surface of the pellets, and then be classified, e.g., by size, so that oversize pellets may be removed from the product.
An example of a device that may perform a combination of the foregoing functions is sold by The Witte Company, 507 Route 31 South. Washington, N.J. 07882-0047 under its model designation “400 Dryer/Cooler/Classifier.” A side view of such example device is shown in FIG. 1, wherein pelletized product, which may be in slurry form in water may be introduced into the device where shown. Water may be removed in a “dewaterer”. The pellets may be dried using forced air in a dryer. Subsequent to drying, the pellets may be cooled by application of forced air. The pellets may then be classified to remove oversized pellets, called “overs.” The pellets are transported through each of the foregoing parts of the device by a conveyor screen. The conveyor screen is configured to move in one direction to transport the pellets, and may be agitated in a direction transverse to the direction of motion of the conveyor screen to reduce piling of the pellets on each other on the screen. Fines may be extracted by suitable air flow through an air discharge outlet located above the dryer/cooler portion of the device.
The device shown in FIG. 1 has proven effective, however there is still a need for improved drying and classifying devices for pellet product manufacturing.